The RFID system described herein is related to the inventions described in commonly assigned U.S. Patent Application Pub. No. 2004/0056091, which is incorporated herein by reference in its entirety. In that patent application, it was pointed out that a need exists for an advertising compliance monitoring system that provides versatility and flexibility by providing an RFID tag, associated with a specific sign or product display, that communicates tag data to an external reader.
U.S. Patent Application Pub. No. 2004/0056091 describes an RFID system that may include RFID tags of various types (e.g., passive, semi-passive or active), backscatter reader transmitters (BRT), and hubs. Typically, each BRT is a fully self-contained, battery operated unit, and utilizes three antennas. Two medium-gain patch antennas are used to read the tags, and a whip antenna is used to report the received data over a wireless link to the hub. This system functions well and is capable of detecting and reporting tags in a variety of retail environments and at different frequencies. It is desirable, however, to provide an even more economical RFID system by centralizing some or all of the electronics that have been distributed across areas or sub-areas in a given facility, thereby reducing redundancy and cost. It is also desirable to increase the read range of tags by the system to reduce the number of antennas required and to increase the reliability of tags being read under marginal conditions.